This dragonfly seemed to have an injured wing and kept fluttering on the sand, the sound of which was what alerted me to it. ID by Jeremy Gatten: "The black spot on the shoulder is diagnostic for Pale Snaketail, once narrowed down to it being a snaketail. The general look - pale blue eyes, green thorax, and yellow pointed marks down the dorsal surface of the abdominal segments - make it a snaketail ... They often land on the ground whereas darners rarely do. Lots of little pointers on this one to work with."